Variable pitch coaxial propeller



g 24, 1954 R. K. TIEDEMAN' 2,687,181

VARIABLE PITCH COAXIAL 'PROPELLER Filed Dec. 1. 1950 5 Sheets-Sheet 1 INVENTQR. ROBERT K.T\EDEMAN ATTORN EYQ g- 1954 R. K. TIEDEMAN VARIABLE PITCH COAXIAL PROPELLER 3 Sheets-Sheet 2 Filed Dec. 1, 1950 INVENTOR. ROBEKT K.T\EDEMAN ATTORNEY.

1954 R. K. TIEDEMAN VARIABLE PITCH COAXIAL PROPELLER 3 Sheets-Sheet 3 Filed Dec. 1, 1950 INVENTOR. ROBERT K.T|ED EMAN ATTO RN EY.

Patented Aug. 24, 1954 VARIABLE PITCH COAXIAL PROPELLER Robert K. Tiedeman, Packanack Lake, N. J., as-

signor to Curtiss- Wright Corporation,

ration of Delaware Application December 1, 1950, Serial No. 198,530

4 Claims.

1 This invention relates to dual rotation controllable pitch propellers for aircraft. Its provisions are particularly applicable to propellers of a dual system which are constrained to rotate at equal or proportional and opposite speeds, and whose blades are intended to operate coincidentally as to pitch change from a single pitch change mechanism.

While not limited to any particular sort of pitch changing mechanism, the invention may be used in conjunction with mechanisms shown and described in copending patent applications Serial Nos. 143,636, filed February 11, 1950 (Mergen and Murphy), 73,586, filed January 29, 1949 (Mergen and Murphy) now U. S. Patent 2,646,131, 34,984, filed June 24, 1948 (Morgen and Tiedeman), and 675,383, filed June 8, 1946 (Chillson). now U. S. Patent 2,640,552.

The invention provides improvements in the means for transmitting pitch changing movement from a pitch changing mechanism through an inboard propeller to the blades of the outboard propeller.

The invention further includes bearing, sealing, and transmission arrangements between inboard and outboard propellers which allow relative articulation without imposing harmful stresses in the mechanism.

The invention further comprises an adjustable but normally stationary pitch control gear inboard of the inboard propeller. The inboard propeller carries a shaft, parallel to the propeller shaft, having a gear meshing with the control gear; and another gear at its outboard end meshed with a pitch control gear normally rotatable with, but adjustable relative to, the outboard propeller. This outboard pitch control gear is drivably connected to the blades of the outboard propeller. The ratios of the several gears mentioned are arranged to produce the desired rotational relationship of the gears.

Exemplary embodiments of the invention are shown in the annexed drawings, which are not to be construed as limiting the scope of the invention, in which similar reference characters designate similar parts and in which Fig. 1 is a schematic elevation of portions of a dual rotation propeller system showing parts in longitudinal section;

Fig. 2a is an elevation, partly in longitudinal section, of the inboard unit of a dual rotation propeller; and i Fig. 2b is an elevation, partly in longitudinal section, of the outboard unit of a dual rotation propeller.

The invention as shown in Fig. 1 is a simplified more or less schematic arrangement of the invention while Figs. 2a and 21) represent a version whose design details have been developed. This description is readable both on Fig. 1 and on Figs. 2a and 2b, the reference characters for parts having similar function being the same. A housing 4, such as an engine or gear box nose, forms a fixed part of the aircraft, and sleeved propeller shafts 5 and 6 extend therefrom, the shaft being embraced by the shaft 5, and extending outwardly therebeyond. By gearing, well known in the art and lying within the housing 4, the shafts 5 and 6 are constrained, when driven, to rotate in opposite directions and proferably, though not necessarily, at the same rotational speed. An inboard propeller hub l is mounted on the shaft 5 through splines 8 and suitable centering cones and nut, and an outboard propeller hub I0 is mounted on the shaft 6 through splines 9 also on suitable centering cones and nut. Each hub has blade sockets II in which blades [2 are mounted for pitch changing rotation in a suitable manner known in the art. Each blade, at or near its butt, carries a worm wheel [3, the worm wheels of the outboard propeller blades being engaged by worms l4, and those of the inboard propeller blades being engaged by worms I5, the worms being mounted in suitable bearings in respective hubs.

Between the inboard hub l and the housing 4 is a housing l6 containing a pitch changing mechanism, held against rotation by a dowel ll engaging the housing 4. The parts of the mechanism which are germane to this invention include a normally stationary pitch control gear l8 coaxial with the hubs which may be rotated by a meshing pinion, not shown, in either direction, or held stationary, by any of the devices shown in the previously identified patent applications or by other means. The gear 18 is provided with internal teeth It engaging planet pinions 20, meshed in turn with a hub concentric sleeve gear 2| piloted on an extension 22 of the inboard hub. Pinions 20 are freely rotatable on shafts 23, carried by a spider, and freely rotatable pinions 24 are also carried on these shafts, the pinions 24 meshing with a stationary ring gear 25 secured to the housing It, and with a sun gear 26 keyed to the hub extension 22 and consequently to the shaft 5. By this planetary gearing, the sleeve gear 2| is enforced to rotate with the inboard hub when the control gear i8 is stationary, and to advance and retard relative to the hub as the gear I 8 is rotated in one or the other direction. 1

The inboard hub 7 carries a hub-eccentric gear 2i meshing with a hub-concentric gear 28, the latter being rotatable or integral with the sleeve gear 2i. Gear 2? drives a planetary speed reducer 28 mounted in the hub which drives the blade engaging worm l5. The speed reducer includes a sun pinion 30 on the shaft of gear 2! driving pinions 3! on a spider 32 connected to the worm E5, the pinions meshing also with a ring gear 33 secured rigidly to the hub l. The train including the gear 21, the reducer 29 and worm is is duplicated for each blade I2 of the inboard propeller. The mechanism thus far described provides for pitch control of the inboard propeller blades, and is not new, per so.

For pitch changing motion to be transmitted from the control gear l8 to the outboard propeller it, it is necessary to provide gearing having members passing through the inboard propeller. To this end, a lay shaft 38 is journalled in the inboard hub l and for convenience and. space saving, it extends through the worm l5 and gear El although it has no functional relation to these parts. The shaft 38 carries an inboard gear 39 meshed with an external hubconcentric gear lil solid with the normally stationary control gear it. The gears 40, 39 have a ratio R1 relative to each other which as shown is of the order of 6:1, although any suitable ratio may be used. On the outboard end of the shaft is a gear ll meshed with a hub-concentric gear it? embracing the outboard propeller shaft and carried for relative rotation with respect thereto on a bearing 43. The gears 42, 4| have a ratio R2 relative to each other which as shown is of the order of 3:1, although any suitable ratio may be used so long as it bears the proper relationship as noted below with respect to the ratio R1.

For a dual propeller system in which the inboard and outboard propellers rotate in opposite directions at equal speeds, the ratio of RllRz must be equal to 2 in order that the gear 42 will rotate in the same direction and at the same speed as the outboard propeller lil. Considering the gear relationships in another fashion, the shaft rotates on its own axis and around the propeller axis since it is carried by the inboard propeller and since the gear 39 rolls around the gear l To make the gear 42 rotate with the outboard propeller, the gear 41 must be of such diameter as to have twice the peripheral speed of the rim of the gear 39. Stated in another way, either the pitch diameters or the number of teeth in the gears must bear the following relationships:

gear 40 seer 2 gear 39- gear 41 I assemblies 38, it, ii are preferably plural in number and spaced around the inboard propeller l, the number of these units being equal to the number of blades of the inboard propeller.

The gear ll carries an integral gear M meshed with gears 45 mounted on shaft 46 journalled in the outboard hub l0 and in associated housing portions rotatable therewith, certain of these housing portions being indicated at it and being secured in part to a sleeve 4! mounted on and rotatable with the outboard propeller shaft 6. Each shaft 46 drives a planetary speed reducer 48 on the hub [0, the output element of which drives the outboard propeller worm i4 meshed with the worm wheel 13 of each outboard propeller blade E2. The speed reducer 38 is like the speed reducer 29 and consists of a sun pinion 5d keyed or pinned to the shaft 36 engaged by planet pinions 5i mounted on a spider 52, the pinions 5i also being meshed with a ring gear 53 anchored as at 54 within a portion of the propeller hub iii. In Fig. l the spider 52 is formed integral with the worm wheel l l but it may be formed separately therefrom and splined to the worm as in Fig. 2b.

The ratios of the speed reducers 29 and i3 and of the gears 28, 27 and l l, respectively on the inboard and outboard propeller hubs may be equal if desired to provide equal rates of pitch change for the blades of both propellers l and it or, alternatively, as is known in the art, the ratios of these reduction gears may be slightly different in order that the inboard and outboard propellers will have differential pitch change to produce equal thrust from the two propellers since one of the propellers is in the wake of the other.

[Should the propellers l and it be geared to rotate oppositely but at difierent speeds, the gear is must still be driven to rotate at outboard propeller speed when no pitch change is called for. To accomplish this, the ratios between the gears all, 3% and ti, l2 are altered from the arrangements above described. The system herein disclosed is not applicable if the outboard and inboard propellers operate at speeds which are independent of one another; the two propeller hafts must be arranged to operate at definite proportional speeds.

In Figs. 2a and 21; detailed provisions are included for providing bearings and seals, and elastic driving connections where there is relative yield in operation between cooperating parts.

The propellers l and it and their various parts are subject to deflections in operation due to operating stresses. The outboard propeller ill, for instance, may weave relative to the inboard propeller l and the outboard shaft 6 may deflect n various ways relative to the inboard shaft 5.

Means are included to provide concentricity and self-alinement in the pitch changing transmission from the inboard propeller to the outboard, and to localize operating deflection to specific locations. A rugged self-alining pilot bearing 56 is provided between the outboard end of the inboard hub l and the inboard end of the outboard shaft 6. By this hearing, the shaft 6 and the hub l are held concentric at the plane of the bearing 55 even though, outboard of the bearing, the shaft 6 and hub as, with its own coinponents, may deflect and weave. The bearing 56 establishes a center of articulation ill for the outboard elements. A labyrinth seal 53, whose elements are concentric with El, is arranged between housing elements 59 and 68 respectively secure 'with the hubs H3 and l, to allow relative movement (other than rotationally) of the housing elements. Also, th engagements between the gears ll and the gear 1 2 are located substantially in the plane of the bearing 58. As has been noted, the gears M are carried by the inboard hub 1, while the gear 42 is carried by the outboard shaft ii. With the gear engagements substantially in the plane of the bearing 55, articulation and relative movement is enabled between the inboard and outboard gear trains, the articulation occurring by axial sliding of the engaged thereon, an outboard propeller shaft passing t through the inboard shaft and having a propeller mounted thereon outboard of the inboard propeller, a self-alining bearing between the inboard propeller and the outboard shaft, disposed between said propellers and enabling weaving of of said propellers relative to each other about the center of said self-alining bearing, pitch change mechanism for and carried by the inboard propeller, pitch change mechanism for the Outboard propeller carried in part by the inboard propeller and in part by the outboard propeller; said latter mechanism including a gear between the propellers and carried by the outboard propeller, a layshaft journalled in the inboard propeller and spaced from and substantially parallel to the inboard propeller shaft, and a gear on the layshaft engaging said outboard propeller gear substantially in a plane normal to the propeller axes and passing through said bearing.

2. In a dual rotation propeller system, an inboard propeller shaft having a propeller mounted thereon, an outboard propeller shaft passing through the inboard shaft and having a propeller mountedthereon outboard of the inboard propeller, a self-alining bearing between the inboard propeller and the outboard shaft, disposed between said propellers and enabling weaving of said propellers relative to each other about the center of said self-aiming bearing, pitch change mechanism for and carried by the inboard propeller, pitch change mechanism for the outboard propeller carried in part by the inboard propeller and in part by the outboard propeller; said latter mechanism including a gear between the propellers and carried by the outboard propeller, a layshaft journalled in the inboard propeller and spaced from and substantially parallel to the inboard propeller shaft, and a gear on the layshaft engaging said outboard propeller gear, the teeth of said gears extending forwardly and rearwardly and substantially tangent to a circle self -a1ining whose center coincides with the center of said self-aiming bearing.

3. In a dual rotation propeller system, an outboard propeller having a pitch change mechanism including a gear coaxial with the propeller and normally rotatable therewith, an inboard propeller includin a gear coaxial therewith and normally rotatable therewith, said propellers being constrained to oppositerotation at equal speeds and being mounted on concentric shafts, a normally stationary pitch control gear, gearing connecting the control gear to the coaxial gear the inboard propeller; gearing including a layshaft car led by the inboard propeller, a gear on the laysliaft engaging the control gear, and a gear on the outboard end of the layshaft engaging the gear of the outboard propeller; and a selfalining bearing between and having its races secured to said inboard propeller and to the shaft of said outboard propeller, said bearing being concentric with and lying in a plane normal to the propeller shafts, the engagement of the outboard layshaft gear and the outboard coaxial gear lying substantially in said normal plane.

In a dual rotation propeller system, an outboard propeller having a pitch change mechanism including a gear coaxial with the propeller and normally rotatable therewith, an inboard propeller includin a gear coaxial therewith and normally rotatable therewith, said propellers being constrained to opposite rotation at equal speeds and being mounted on concentric shafts, a normally stationary pitch control gear, gearing connecting the control gear to the coaxial gear of the inboard propeller; gearing including a layshaft carried by the inboard propeller, a gear on the layshaft engaging the control gear, and a gear on the outboard end of the layshaft engaging the gear of the outboard propeller; and a bearing between and having its races secured to said inboard propeller and to the shaft of said outboard propeller, said bearing being concentric with and lying in a plane normal to the propeller shafts, the engagement of the layshaft gear and the outboard coaxial gear meshing on lines substantially tangent to a construction sphere concentric with said self-alining bearing.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,232,683 Lloyd Feb. 25, 1941 2,236,841 Waseige Apr. 1, 1941 2,305,454 Nallinger et al Dec. 15, 1942 2,367,230 McCoy Jan. 16, 1945 FOREIGN PATENTS Number Country Date 550,354 Great Britain Jan, 5, 1943 915,163 France July 16, 1946 

